The long-term goal is to investigate and develop in vivo proton magnetic resonance spectroscopy (MRS) for early diagnosis and management of breast cancer. The short-term objective is to develop a spectroscopic imaging method Sel-MQC (Selective Multiple-Quantum Coherence transfer) that permits non-invasive proton detection of metabolites and unsaturated fatty acids in breast tissue with clinical acceptable time efficiency and spatial resolution. Robust suppression of the intensive signals from lipid and water will be achieved in a single scan. The metabolite and lipid molecules will be subsequently investigated as molecular markers to differentiate benign and malignant human breast tumors. Our aims in this grant period are: (1) To develop and implement the Sel-MQC methods on a low field 2.1T human MRI/MRS spectrometer. Both low-strength commercial magnetic field gradients or strong specifically built local magnetic field gradients will be employed for efficient coherence selection and filtering. Protocols will be established for detection of lactate, choline, and unsaturated lipid molecules in breast cancer patients. (2) To develop multi-slice modules of the Sel-MQC sequences using Hadmard matrix approach to improve spatial resolution in monitoring metabolic changes in human breast cancer. The project will extend in vivo proton MRS beyond current limit of examining metabolites inside brain. Detection of tumor-specific molecules and differentiation of malignant and benign breast lesions in pre-invasive stage (possibly before any morphological changes) by proton MRS will improve the efficiency of breast cancer therapy and the cost-effectiveness of breast cancer care. The proposed method will have wider applications in other organs.